Steam has been used for many years in the production of electric power. In particular, geothermal sources of steam have increasingly been utilized in recent times as sources of energy. Conventionally, steam turbines are used to convert geothermal steam exiting wells into electric power.
Recently, more extensive use of this source of energy has been achieved by using closed organic Rankine cycle turbines and quite often, a combination of steam turbines and closed organic rankine cycle turbines has been used in the production of power from these geothermal sources which many times contain non-condensable gases, for example carbon dioxide, hydrogen sulfide, etc., detrimental to the environment. Such a system is disclosed in U.S. Pat. No. 4,542,625, the disclosure of which is hereby incorporated by reference, where a steam condenser operating at pressure greater than atmospheric pressure is used to condense heat depleted steam exiting a steam turbine and collect the non-condensable gases by applying an organic fluid which is vaporized for use in running a closed organic cycle Rankine turbine. Subsequently, the condensate together with the non-condensable gases having been compressed are pumped back into a reinjection well rather than exhausting the gases into the free atmosphere. In such cases, it has been conventional to use one or more large steam turbines to produce power from the geothermal steam exiting the wells with a larger number of separate closed organic Rankine cycle turbines operating on the heat depleted steam exiting the steam turbines. A power plant of this type thus requires a rather extensive and costly distribution system having large diameter conduits for supplying the low pressure, heat depleted steam exiting the steam turbines to the closed organic cycle Rankine turbines and a reasonably sophisticated control system, since for example, the heat depleted steam must be handled even in the case of malfunction or closing down of one or more of the organic Rankine turbines. Furthermore, the malfunction or closing down of one or more of the organic Rankine turbines or even the reduction of the output of one or more of the organic Rankine turbines also normally causes a reduction in the operating efficiency of the steam turbines as the organic fluid acts as the cooling fluid of the steam condensers.
It is therefore an object of the present invention to provide a new and improved method of and apparatus for producing power from steam wherein the disadvantages as outlined are reduced or substantially overcome.